A “Toolbox” for Forensic Engineers

Failure of Medical Implements 289
be working to an intended performance criterion along with a set of design
requirements to meet in-service demands. Minimum performance and
design requirements can be described as follows.
9.3.1 Performance
The intended performance of a medical device or tool can be described by
addressing its
• Functional characteristics
• Intended in-service conditions of use
Account has to be taken of any published standards, clinical and scientific
literature and any validated test results.
9.3.2 Design Attributes
To meet performance benchmarks, the development of applicable design
attributes has to consider the following points as a minimum:
1. Physical, mechanical and chemical properties of the instrument materials;
microbiological and particulate contamination levels; the ease
of use, cleaning and maintenance
2. The potential deterioration of the material characteristics due to sterilization
and storage
3. The effect of contact between the instrument and body environment,
or the implant and other instruments
4. Shape and dimensions, to include their possible effects on the body
5. Wear characteristics of materials and the effect of wear products on
the instrument or body
6. Insertion, removal and interconnecting parts
7. Extent of fluid leakage and/or diffusion of substances into or out of
instruments; leaching of chemical species out of the implant
8. The accuracy and stability of instruments with a measuring function
9. The ability of the implant, instrument or fragment of an instrument
to be located by means of an external imaging device
Application of performance and design criteria is intended to minimize
any likelihood of premature failure. Needless to say, any design solution will
be evaluated prior to introduction (preclinical) in addition to in-service
(clinical) assessment. As with any engineered artifact, the critical engineering
issues applicable to premature failure in a medical device or tool are design,
material selection and biocompatibility.